Visualization and Measurements of Sub-Millisecond Transient Spray Dynamics Applicable to Direct Injection Gasoline Engine : Part 1:Visualization of Spray Using High Speed Video Camera and Laser Sheet Technique

Transient temporal and spatial spray characteristics have been investigated. A kind of practical fuel injector with swirl nozzle was examined under variable injection duration within the range of 0.25 to 4.0 ms and injection pressure 5.0 and 7.0 MPa. The fuel spray was injected at a cycling frequency of 50 Hz in a room under normal atmospheric condition. Considered details of sub-millisecond transient dynamics were observed by using a high-speed video camera with temporal resolution of 24.69 μs (40 500 frames/s). The results indicate that investigated spray consists of two incorporated flow fractions that are a core jet and a quasi -umbrella droplets spray simultaneously moving down and swirling in local cross-axis domains. Instantaneous transient values of axial and radial penetration were accurately evaluated and analyzed. It was observed that after actual injection a post injection of fuel droplets occurs and the time delay and lifetime of these droplets were systematically estimated.